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SubjectRe: [PATCH 2/3] mm/mlock: prepare params outside critical region
On 10/18/2013 02:50 AM, Davidlohr Bueso wrote:
> All mlock related syscalls prepare lock limits, lengths and
> start parameters with the mmap_sem held. Move this logic
> outside of the critical region. For the case of mlock, continue
> incrementing the amount already locked by mm->locked_vm with
> the rwsem taken.
>
> Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
> Cc: Michel Lespinasse <walken@google.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> mm/mlock.c | 18 +++++++++++-------
> 1 file changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/mm/mlock.c b/mm/mlock.c
> index d480cd6..aa7de13 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -689,19 +689,21 @@ SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
>
> lru_add_drain_all(); /* flush pagevec */
>
> - down_write(&current->mm->mmap_sem);
> len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
> start &= PAGE_MASK;
>
> - locked = len >> PAGE_SHIFT;
> - locked += current->mm->locked_vm;
> -
> lock_limit = rlimit(RLIMIT_MEMLOCK);
> lock_limit >>= PAGE_SHIFT;
> + locked = len >> PAGE_SHIFT;
> +
> + down_write(&current->mm->mmap_sem);
> +
> + locked += current->mm->locked_vm;
>
> /* check against resource limits */
> if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
> error = do_mlock(start, len, 1);
> +
> up_write(&current->mm->mmap_sem);
> if (!error)
> error = __mm_populate(start, len, 0);
> @@ -712,11 +714,13 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
> {
> int ret;
>
> - down_write(&current->mm->mmap_sem);
> len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
> start &= PAGE_MASK;
> +
> + down_write(&current->mm->mmap_sem);
> ret = do_mlock(start, len, 0);
> up_write(&current->mm->mmap_sem);
> +
> return ret;
> }
>
> @@ -761,12 +765,12 @@ SYSCALL_DEFINE1(mlockall, int, flags)
> if (flags & MCL_CURRENT)
> lru_add_drain_all(); /* flush pagevec */
>
> - down_write(&current->mm->mmap_sem);
> -
> lock_limit = rlimit(RLIMIT_MEMLOCK);
> lock_limit >>= PAGE_SHIFT;
>
> ret = -ENOMEM;
> + down_write(&current->mm->mmap_sem);
> +
> if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
> capable(CAP_IPC_LOCK))
> ret = do_mlockall(flags);
>



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